FIG. 13 shows an example of a known completely-split mechanical seal in which a static seal ring and a rotating seal ring are split along the circumferential direction thereof in a mechanical seal (see Patent Document 1, for example; hereinafter referred to as Prior Art 1).
FIG. 14 shows a known partial split mechanical seal in which a static seal ring is bound and retained in an annular state by the elastic force of a binding body composed of an elastic material charged between the opposing peripheral surfaces of a retainer and the static seal ring in a split mechanical seal, in which a static seal ring on the side of a seal case is split in the peripheral direction thereof and fitted into and held by a retainer in an annular state in which the divided faces thereof abut each other, and a shielding seal is formed between a sealed fluid region and a non-sealed fluid region by the relative rotational sliding of the sealing end surfaces that are the opposing end surfaces of the static seal ring and a rotating seal ring on a rotary shaft side, the sealed fluid region being the region on the internal peripheral side of a relatively rotating and sliding portion, and the non-sealed fluid region being the region on the external peripheral side of the relatively rotating and sliding portion (see Patent Document 2, for example; hereinafter referred to as Prior Art 2).
The completely split mechanical seal of Prior Art 1 shown in FIG. 13 comprises a seat ring 75 integrally fastened to an overhanging end surface of a fixed casing 70; a seal ring 77 loosely fitted on a rotary shaft 71 inserted through the fixed casing 70, so that a sliding seal surface S is formed against the adjacent seat ring 75; a shaft packing 87 enclosed in a gap formed between the internal peripheral surface of the seal ring 77 and the external peripheral surface of the rotary shaft 71; a seal ring holder 78 for embracing the external peripheral surface of the seal ring 77; a holder band 79 for further embracing the external peripheral surface of the holder 78; a retainer ring 80 integrally fastened to the seal ring holder 78 so as to confine the back end surface of the seal ring 77; a drive ring 82 integrally fitted on the rotary shaft 71, and integrally coupled to the retainer ring 80 via a drive pin 84; and a compression coil spring 85 inserted between mutually adjacent surfaces of the drive ring 82 and the retainer ring 80 so as to impart a back pressure to the seal ring 77. The shaft packing 87 and the holder band 79 both form a C-shape in which expansion deformation is possible, whereas the seat ring 75, seal ring 77, seal ring holder 78, retainer ring 80, and drive ring 82 are divided into two sections entirely facing each other, and are integrally fastened so as to be detachable at the divided faces thereof, and the divided face of at least the seal ring 77 and the divided face of the seal ring holder 78 differ in phase from each other by an arbitrary intersection angle. In this completely split mechanical seal, seat ring segments of the seat ring 75 that is divided into two sections are integrally fastened in an overall circular ring shape by a bolt 89 and a tapered-pin-type centering wedge 92 inserted at the divided face; and retainer ring segments of the retainer ring 80 that is divided into two sections are integrally fastened in an overall circular ring shape by a bolt 123 and a tapered-pin-type centering wedge 126 inserted at the divided face.
In the partial split mechanical seal according to Prior Art 2 shown in FIG. 14, a static seal ring 69 divided in the peripheral direction thereof is bound and retained in an annular state with the divided faces thereof abutting each other by the elastic force of a binding body 88 composed of an elastic material charged between the external peripheral surface 69c of the static seal ring 69 and the internal peripheral surfaces 85a, 85b of a retainer 7 composed of a cylindrical first retainer member 84 retained by a seal case for fittingly retaining the static seal ring 69, and a cylindrical second retainer member 85 for fittingly retaining the seal ring 69, the second retainer member 85 being attached so as to be fastenable to the first retainer member 84 in the axial direction. The binding body 88 is composed of rubber, synthetic resin, or another incompressible elastic material.